The lawyers argue that FBI informants entrapped their clients. They say the discussions amounted to little more than a religious debate about jihad.
They will also challenge the constitutionality of a Patriot Act provision used to seize video the defendants left at a store for reformatting.
The footage shows the defendants firing assault weapons and screaming about jihad.
Federal prosecutors acknowledge the men did not necessarily have a specific plan to attack Fort Dix.
Four of the young men are serving life terms. They lived in Philadelphia and suburban New Jersey.
The arguments are set for Monday in US appeals court in Philadelphia.
