He graduated from Faculty of Law of University of Latvia in 1993 and afterwards worked in prosecutor's office and court of Liepāja city.

He was elected to the 8th Saeima and was head of the parliamentarian Law committee, a position he retained after being re-elected to the 9th Saeima, when he also became head of parliamentarian National security committee.

He was widely cited in newspapers on February 20, 2008, following a 34-year-old English man being jailed in Riga for urinating on the historic Freedom Monument.

Seglins described the British people who cause trouble in Latvia when inebriated, typically on weekends away for parties such as stag nights, as "pigs".

In March 2009, Seglins became the minister of justice in Valdis Dombrovskis' cabinet.