States on both sides of the issue are asking the high court for clarification.
Pennsylvania Gov. Tom Corbett said he must follow how courts interpret laws.
Medical marijuana has broad support, but people are divided over recreational use.
The move makes the state the 18th to legalize gay marriage.
More than 900 same-sex couples had wed in the state since Dec. 20.
A federal judge on Wednesday ruled that Colorado’s ban on same-sex marriage is unconstitutional.
Ohio officials are expected to appeal the ruling.
The ruling in Michigan came one day after a judge ruled the law was unconstitutional.
He said state officials are not obligated to defend discriminatory statutes.
His home state will become the 15th state to legalize same-sex marriage.