HARTFORD, April 20 - Gov. M. Jodi Rell on Wednesday signed into law a measure allowing same-sex couples to enter into civil unions, making Connecticut the second state after Vermont to approve such unions and the first to do so without pressure from the courts.

"I think that it certainly bodes well for Connecticut that we didn't have to be ordered to do this," said Mrs. Rell, a Republican, who signed the bill about an hour after the Democratic-controlled Senate approved the measure by a three to one ratio. The House passed the bill last week 85 to 63.

Under the law, which takes effect on Oct. 1, couples in civil unions will essentially have all of the rights and protections the state provides married couples, from tax benefits and insurance coverage to hospital visiting rights to family leave from work.

The law also includes an amendment, added last week, that defines marriage as being between a man and a woman.