St. Maxent, whose fortune was tied to France, was to have his loyalties severely tested in the transition from French to Spanish control.
When the Creole and German settlers around New Orleans resisted Spanish rule in the Rebellion of 1768, they imprisoned St. Maxent at his plantation from October 25 to 29, 1768, releasing him after Ulloa was forced out of the city to return to Spain.
In January 1769, St. Maxent thwarted the plotters' efforts to enlist Native Americans in the planned resistance to any Spanish attempt to reclaim New Orleans.
In August 1769, Alejandro O'Reilly restored Spanish authority in New Orleans, putting down the rebellion and executing five ringleaders while imprisoning five others.
In 1782, he traveled to Spain to get concessions from King Carlos III, including permission to import slaves without paying duty.
While returning to Louisiana in 1782, his two ships and crew were captured by British naval forces and sent to Kingston, Jamaica, where St. Maxent was held under house arrest and his men put in prison.
One of his British benefactors was arrested in Havana, St. Maxent was implicated in smuggling specie (gold), and the Spanish revoked his titles and embargoed his property.
The next Spanish governor, Francisco Luis Héctor de Carondelet, called him back to military duty to help build Fort San Felipe.