A federal judge here ruled yesterday that, while he was sympathetic to the claims of 2,500 people suing the Mexican government over 200-year-old land claims in Texas, he could not intervene in a matter delegated by the Constitution to the executive and legislative branches.

The descendants of original holders of claims to 12 million acres of land in Texas deeded by Spain or Mexico filed suit here last September seeking to force the Mexican government, which has recognized its indebtedness, to pay the claims. Those claims could amount to nearly $1 billion.

After the U.S.-Mexican War in 1848, the original claimants and their families were either run off their land during Indian wars or denied access to it by new settlers in Texas in the late 19th century.

A 1941 treaty between the United States and Mexico ended in an exchange of claims between the two countries and obligated Mexico to compensate the heirs, according to the claimants' suit. But the Mexican government has refused to pay.

U.S. District Court Judge Thomas F. Hogan said he was sympathetic to their dilemma and that the "alleged delays on Mexico's part offend his sense of fair play and justice."

However, Hogan said he is empowered neither to order Mexico to pay the claims nor to take any action, such as attaching Mexican assets in the United States.

Hogan said the issue involves "high-level policy judgments, requiring deference to the expertise and discretion of the U.S. Congress and the executive branch."

He said he must defer to "the expertise of the Mexican government" in determining how much compensation each claimant should receive, "regardless of whether that judgment . . . is an abuse of discretion."

Hogan said that several considerations, including provisions of the Foreign Sovereign Immunities Act, prevent him from taking any action to resolve what he concluded are "internal obligations" of the government of Mexico.