Utah's legislature approved a state redistricting plan today and the reaction was predictable: Democrats denounced it as blatant and dastardly gerrymandering while Republicans maintained they were merely following the will of the people.

Both parties did agree that the plan, approved at the end of a three-day special session of Utah's Republican-dominated legislature, probably will put Utah's three congressional seats into Republican hands for the next 10 years. Gov. Scott Matheson, a Democrat, is expected to veto the redistricting bill, however, and if the legislature overrides his veto the case probably will end up in court.

Matheson called the special session to draw new boundaries for the three congressional seats to which the state is now entitled because the 1980 census increased Utah's House seats from two to three.

Matheson had appointed a bipartisan commission of four Republicans and three Democrats to study redistricting for the seats and for the state legislature.

But Republicans announced in advance that drawing boundaries was the legislature's business, and they repeated that assertion when the commission, after statewide hearings and studies, submitted a report about two weeks ago.

The Republican legislators drew a line in Salt Lake County that meandered north-south along the Jordan River and placed a predominantly Democratic area in the new 3rd District along with overwhelmingly Republican counties. This also meant that more Republican voters would remain in the 2nd District, now represented by Republican Rep. David D. (Dan) Marriott.

"The reapportionment committee did exactly what Dan Marriott asked it to do," charged Democratic state Sen. Omar Bunnell. "We call it the Marriott Line, something like the Maginot Line."

"You can call it the Marriott Line if you wish," countered Sen. Fred Finlinson, Republican chairman of the reapportionment committee. "But it's the committee line and the fact that Mr. Marriott agreed with it is coincidental. The people of Utah elected more Republicans to the legislature and we should have them vote on it."