A U.S. District Court judge today said he would not issue an injunction sought by Conoco Inc. that would have barred the big Canadian distiller, Seagram Co., from making a takeover bid for the nation's ninth-largest oil company.

Conoco, which wants to merge with the big chemical company E.I. duPont de Nemours & Co., alleged that Seagram had promised not to make an unfriendly offer for the oil giant after Conoco's board of directors spurned an offer by Seagram to buy 25 percent of Conoco stock.

Judge Edward Weinfeld said that Conoco shareholders should have the right to consider both the Seagram offer (to buy up to 51 percent of Conoco stock at $85 a share) and the Du Pont bid (to pay $95 a share for 40 percent of Conoco stock and 1.7 shares of Du Pont for each of the remaining Conoco shares).

In other developments, a House subcommittee today passed by a voice vote a bill that would put a 180-day moratorium on acquisitions by foreigners of more than 5 percent of the stock of a U.S. company that holds mineral leases on federal lands. The bill, passed by the mining subcommittee of the Committee on Interior and Insular Affairs, would be retroactive to all purchases after July 15.

A subcommittee aide said that if the bill should become law as passed today it not only would affect the Seagram bid for Conoco, but also the $2.74 billion takeover of Texasgulf Inc. by the French-owned Societe Nationale Elf Aquitaine.

Another House subcommittee today adopted a bill that would impose restrictions on how much foreign investors may borrow to finance a takeover attempt but refrained from acting on a moratorium proposal that the administration has opposed.

At the same time, Energy and Commerce Committee Chairman John D. Dingell (D-Mich.) and 16 other committee members warned President Reagan that Congress may have to take stronger actions in response to the threat to American economic interests if the administration cannot win concessions from the Canadian government.

The letter stated that Canadian policies that put U.S. firms at a competitive disadvantage "require action to protect the legitimate investments and business activities of U.S. citizens." Dingell and the others called upon Reagan to make U.S. concerns clear at the Ottawa economic summit next week.