AUSTIN - Gov. Rick Perry's lawyers filed a motion Monday to bar prosecution of the governor "on multiple constitutional grounds."

Perry faces a felony indictment accusing him of abusing his veto power to try to force the ouster of the Travis County district attorney after her drunken driving arrest.

The writ of habeas corpus seeks to dismiss the indictment against Perry and to bar any further prosecution.

It contains the theme pushed by the Republican governor and his team that his prosecution is a political one. That idea that has been rebuffed by the special prosecutor, San Antonio lawyer Michael McCrum.

The filing cites the constitutional separation of powers among the branches of government and Perry's free-speech rights.

"Subjecting any sitting governor to a criminal prosecution and injecting the judiciary into a political dispute would be an unprecedented assault on this cherished separation of powers
and impose an intolerable and incalculable chilling effect on the free exercise of legitimate constitutional powers by future governors," it said.

It said that the prosecution violates Perry's free-speech rights by "seeking to criminalize not merely the veto itself but the governor's explanation for it, as well."

"These violations are contrary both to Texas' commitment to open, transparent government and to the people's right to be fully informed about their governor's (thought) processes in fulfilling one of his core governing duties," it said.

The filing also complains about the laws used in Perry's indictment.

The case against Perry involves his threat last year to veto funding for a public corruption unit overseen by Democratic Travis County District Attorney Rosemary Lehmberg unless she resigned in the wake of a messy drunken-driving arrest and guilty plea.

Lehmberg served time but stayed in office. The Republican governor vetoed the money for the unit, saying Lehmberg had lost the public's confidence.

Texans for Public Justice, a liberal government accountability group, filed a criminal complaint. It didn't question Perry's right to veto the funding, but said the governor was wrong to use his power to try to force out a locally elected official.

A grand jury indicted Perry on Aug. 15 on two counts: abuse of official capacity, a first-degree felony punishable by five to 99 years in prison; and coercion of a public servant, a third-degree felony carrying a punishment of two to 10 years in prison.

The writ filed by Perry's lawyers said the coercion measure is "fatally vague and overbroad" and fails "to give reasonable notice to any official about what is permissible conduct on the one hand and what is felonious conduct on the other."

The filing said both measures "are vague and overbroad as applied to this case."