BOSTON (AP) — President Barack Obama made a Labor Day visit to Boston on Monday to reinforce ties with unions, fellow Democrats and the city he knew as a law student.

Speaking at the annual union breakfast, Obama announced an executive order requiring federal contractors to give their workers paid sick leave. It comes two months after a Massachusetts state sick leave law took effect.

The president got a bipartisan greeting at Logan International Airport from Republican Gov. Charlie Baker and Boston’s Democratic mayor, Marty Walsh. Democratic U.S. Sen. Elizabeth Warren, who has sometimes clashed with Obama on economic issues, warmed up the breakfast crowd before he arrived.

Outside the breakfast, transit union workers protested Baker’s plan to privatize some MBTA bus routes, and picketing cab drivers demanded regulation of ride-hailing services such as Uber.

Obama, speaking in a casual button-down shirt, referred to the city’s most popular union member, New England Patriots quarterback Tom Brady, whose four-game “Deflategate” league suspension was successfully challenged in court last week by the players’ association.

“Brady’s happy he’s got a union,” Obama said. “They have his back.”

Obama recalled his days as a Harvard Law School student stuck in the library most of the time and his warm welcome at the 2004 Democratic National Convention in Boston as “an unknown state senator with a funny name.”

On his way to the airport, Obama made a stop at Union Oyster House near Faneuil Hall to order 10 chowders to go.

Several New England members of Congress, including Warren, Sen. Edward Markey, Reps. Katherine Clark and Seth Moulton of Massachusetts, and New Hampshire Rep. Ann McLean Kuster, got a ride back to Washington with the president.

The Massachusetts Republican Party issued a statement in connection with his visit, saying the tax related to the health care law on high-cost employer health insurance plans taking effect in two years will affect many union members and should be eliminated.