Just one day after he resigned the federal post he held for nearly seven years, former U.S. Attorney Patrick L. Meehan announced Wednesday that he is joining Conrad O’Brien Gellman & Rohn, a 40-lawyer litigation boutique in Philadelphia, to launch a corporate and white-collar criminal practice, effective next Monday.

In an interview, Meehan, 52, said that when he began exploring his options in discussions with friends and advisers, the Conrad O’Brien firm came up again and again.