On January 20, 2022, Bullock was appointed by Secretary of the Interior Deb Haaland to the inaugural board of directors of the Foundation for America's Public Lands.

[10] Under Bullock, the Attorney General's office initiated the 24/7 Sobriety Program which requires repeat DUI offenders to take daily alcohol tests.

[11] The Attorney General's office also pursued the railroad industry for monopolistic business practices[12][13] and took part in a 16 state effort to urge the federal government to use antitrust authority against consolidation in agriculture.

[14] Bullock focused on the misclassification of employees as independent contractors and allowing FedEx to avoid paying millions in state taxes and fees.

[15] Bullock attracted national attention by challenging the Citizens United decision through his defense of Montana's 100-year-old ban on corporate campaign expenditures.

[22] Bullock pledged to give Montana homeowners a one-time $400 property tax rebate to refund a portion of the state's $400 million budget surplus.

In November 2015, McLean announced her resignation as lieutenant governor, effective upon the appointment of her successor, in order to accept the position of director of American Indian and minority achievement in the office of the state commissioner of higher education.

[43] In July, Bullock issued a statewide face mask mandate for indoor public places and large outdoor gatherings.

[47] In 2017 Bullock formed the Big Sky Values PAC, which by spring 2019 had raised nearly $1.8 million, to pay for travel around the United States.

[49][50] In his announcement video, Bullock said that opposing political "dark money" and legislating against the Citizens United Supreme Court ruling would be among his utmost priorities.

[51] Based on his three statewide electoral victories in a Republican-leaning, largely rural state, Bullock held a certain cachet of "electability", and appeared to have a plausible path to the nomination.

[53] Even so, the late start left him with less media exposure than his numerous rivals: he found it hard to raise funds, and never rose above 1% in nationwide polls.

[59] However, Bullock's entrance shifted the dynamics of the contest; many political pundits then considered it a competitive race and a potential pickup for Democrats.

[69] In 2017, Bullock vetoed measures to outlaw abortions after 20 weeks, citing constitutional rulings on the women's ability to protect their lives and health and arguing that elected officials should not put personal beliefs above medical professionals' judgment.

The Supreme Court disposed of the case in a 5–4 decision,[74] but Bullock continued to advocate for campaign finance reform throughout his time as governor of Montana.

[75][76] In 2015, Bullock steered the DISCLOSE Act, a bipartisan campaign finance reform bill that bolstered disclosure requirements in Montana elections, through a GOP-controlled state legislature.

[78] On July 24, 2018, Bullock sued the Internal Revenue Service and the U.S. Department of the Treasury[79] over a recent decision to dispense with donor requirements for nonprofit organizations.

[82] In September 2014, Bullock signed an executive order creating a habitat conservation plan for sage-grouse in a bid to keep management of the imperiled bird in state hands rather than see it come under federal Endangered Species Act protection.

[87][88] He visited Iowa,[89] Wisconsin,[90] and Colorado[91] to speak in support of Democratic candidates during the 2018 election cycle, leading some to speculate, correctly, that he was considering a presidential run.

[92] In 2019, Bullock said he supports the death penalty in "limited circumstances" like terrorism—a stance that distinguished him from the crowded 2020 Democratic presidential field.

[96][97] In the wake of the Stoneman Douglas High School shooting, he also reversed his opposition to banning assault weapons, saying they were rarely used for hunting or self-defense.

[94][95] He continues to oppose measures such as mandatory gun registration, and has suggested that extreme proposals by Democrats may play into the hands of industry lobbyists.

[100][101] In 2015, Bullock supported a federal decision to allow the admission of Syrian refugees, despite pushback from Republican state legislators; he promised that ensuring the safety of Montanans would be his "top priority" and that the vetting process was "extraordinarily thorough".

"[97][103] In 2018, Bullock refused to deploy National Guard troops from Montana to the Mexican border "based simply on the whim of the President's morning Twitter habit.

[111] The executive order expanded upon one signed by Governor Brian Schweitzer in 2008, which had similar goals but did not include protections for gender identity and did not apply to contractors or subcontractors.

[113] On January 22, 2018, Bullock signed an executive order prohibiting any internet service provider with a state government contract from blocking or charging additional fees for faster delivery of websites, two major principles of net neutrality.

Bullock opposes right-to-work legislation,[123] which allows workers to forgo paying union dues while still benefitting from union-negotiated labor contracts.

[123] On January 18, 2018, Bullock filed an amicus brief to the U.S. Supreme Court in support of allowing labor unions to make "agency fees" mandatory.