The Media Marketing Accountability Act would give the Federal Trade Commission (FTC) the power to punish film distributors who break the industry's code of practice by aiming promotional campaigns for adult films at children.
Baldwin, who is president of pressure group The Creative Coalition, says the proposed law would give the government too much power over the type of entertainment made.
But Senator Joseph Lieberman, who proposed the legislation, says it will make Hollywood accountable for the influence of violent films on children.
The Media Marketing Accountability Act would give the Federal Trade Commission (FTC) the power to punish film distributors who break the industry's code of practice by aiming promotional campaigns for adult films at children.
The Creative Coalition sent a letter to Bush this week saying the bill goes against the American constitution's first amendment right to free speech, according to trade newspaper Variety.
'Dangerous'
"The government would, in effect, have enormous and inappropriate clout on the kind of entertainment that is produced," Baldwin told the newspaper.
Senator Lieberman's stance sets a "dangerous precedent", according to Baldwin, who has starred in Backdraft and Flatliners and is brother of actor Alec Baldwin.
He says the government should not have the power to police the marketing of creative material.
The Creative Coalition sent a letter signed by more than 50 arts and entertainment professionals to Senator Lieberman and other politicians last month.
But Senator Lieberman has also appealed to the president for support. The bill is also backed by Senator Hillary Clinton, wife of former president Bill Clinton.
Limited authority
The Connecticut senator has expressed his concern that the entertainment business is actively marketing adult films to younger viewers.
The bill would give the Federal Trade Commission (FTC) limited authority to pursue the industry for violations.
It would also prevent entertainment companies from engaging in advertising or marketing that is intentionally directed at minors or presented in child-orientated venues.
Senator Lieberman's views were shared by an FTC report, which put forward the concept of voluntary marketing codes.
But a subsequent report found that only the games industry had agreed to adopt the code.