NEW YORK, Aug 8 (Reuters) - Reasoning that the law regarding Miranda rights changed following a 2010 Supreme Court decision, a U.S. appeals court on Monday reversed itself in a case involving a suspect's statements to the police.

The unanimous 2nd U.S. Circuit Court of Appeals opinion appears to be the first time a federal appeals court has changed direction as a result of last year's Supreme Court decision that found suspects must explicitly assert their legal right to remain silent.

The case in question involves statements suspect Gordon Plugh made to police after he was arrested in Sept. 2005 in Wayland, New York on child pornography charges.

According to the opinion, Plugh upon his arrest was immediately advised of his Miranda rights -- which inform a suspect of his right to remain silent and to an attorney. He at first refused to sign a waiver-of-rights form, where a suspect can waive his right to a lawyer during questioning. Hours later, however, Plugh began to talk and signed the waiver.

The district court, which was upheld by the 2nd circuit at the time, said these subsequent statements could not be used against Plugh at trial because his initial refusal to sign the form meant he was invoking his Miranda rights.

"The agents should have ceased all questioning in the face of that refusal to sign the form and suppressed the ensuing statements," the opinion said of its reasoning at the time.

On Monday, the circuit changed its mind.

"Critically, at no point did Plugh unambiguously inform the custodial officers that he wished to invoke his right to remain silent or his right to speak with an attorney, nor was his course of conduct such that the officers should reasonably have been put on notice that... no further questioning could occur," wrote Judge Debra Ann Livingston in the opinion.

"In sum, therefore, we hold, consistent with Berghuis, that for a defendant to invoke either the right to remain silent or the right to counsel, he must do so unambiguously, and that a refusal to sign a waiver of those rights, however unequivocal, is not itself necessarily sufficient to establish an unambiguous invocation thereof."

Defense attorney Gerald Shargel said the circuit had further eroded suspects' rights.

"This obviously is a watershed moment because it further erodes the miranda rule because it seems to rely on the formality of the assertion of rights rather than what happened in the circumstances," Shargel said.

But Kent Scheidegger of the Criminal Justice Legal Foundation in California said the 2nd circuit had erred the first time and was correct in its opinion.

"The basic, real constitutional requirement is that a person not be compelled to be a witness against himself," Scheidegger said."Plugh clearly was not compelled."

The case is U.S., et al v. Gordon Plugh, 2nd U.S. Circuit Court of Appeals, No. 10-2815.

For U.S.: Joseph Karaszewski, Assitant U.S. Attorney, Western District of New York.

For Plugh: Jeffrey Wicks of Rochester, NY.

(Reporting by Basil Katz)