By Jane Sutton

GUANTANAMO BAY U.S. NAVAL BASE, Cuba (Reuters) - The Guantanamo prison warden testified on Thursday that he banned defense lawyers from bringing spiral notebooks into client meetings because the metal spirals could be removed and made into garrotes.

He appeared ready to demonstrate when the judge in the Guantanamo war crimes tribunal blocked him from field-stripping a red notebook on the witness stand.

The debate over the danger of spiral notebooks came as defense lawyers for an alleged al Qaeda bomb plotter argued that prison rules are arbitrary and capricious and interfere with efforts to prepare a defense in a case that could end with the execution of defendant Abd al Rahim al Nashiri.

Nashiri, a 48-year-old Saudi, is accused of directing suicide bombers to ram a boat full of explosives into the side of the USS Cole off Yemen in 2000, causing a blast that killed 17 U.S. sailors and injured dozens more.

In pretrial hearings this week at the Guantanamo Bay U.S. Naval Base, defense attorney Rick Kammen said he had for years been allowed to bring large spiral notebooks into the prison camp to make notes during meetings with Nashiri.

With staples and paper clips prohibited, the numbered notebooks kept his papers organized and allowed him to easily refer to notes from earlier meetings, he said.

Army Colonel John Bogdan, a military policeman with years of experience running jails, assumed the warden's role in June 2012 and banned spiral notebooks because "the wire in it can be used to form a garrote or a weapon," he testified.

Kammen said guards monitor the attorney-client meetings via cameras able to zoom in close enough to read words on paper and would surely step in quickly if they saw anyone stripping spirals.

He handed Bogdan the red notebook and said, "In order to reasonably demonstrate the frivolousness of the colonel's position we'd like to see how long it takes."

The judge, Army Colonel James Pohl, halted the demonstration but asked Bogdan if the ban covered notebooks with plastic spirals.

"If the plastic would be firm and strong, yes," Bogdan said. Asked whether three-ring binders would be acceptable, Bogdan said he would have to examine the binder in question before answering that.

Kammen urged the judge to issue an order allowing him to keep using metal spiral notebooks. Prosecutors urged the judge to stay out of the matter and let Bogdan make the prison rules. The judge did not indicate when he would rule.

The hearing is scheduled to continue on Friday in a closed session to discuss matters so secret that Nashiri will not be allowed to attend because he lacks a U.S. security clearance.

Thursday's hearing also addressed weighty topics such as whether terrorism is a stand-alone offense or a broad category of crimes, and whether anyone is listening in to attorney-client meetings that are supposed to be confidential. Bogdan testified that no one did.

Nashiri has been in U.S. custody since his capture in Dubai in 2002 and was first charged in the Guantanamo tribunals in 2008. It was unclear when his trial would start.

(Editing by Kevin Gray and Doina Chiacu)