A Marshall Islands advisor says moves by the Marshalls and US governments to push through a new agreement for long-term use by the US of the missile testing range on Kwajalein is unconstitutional.
Government officials say landowner opposition to the agreement will not delay implementation of the Compact of Free Association.
The Compact provides the Marshall Islands with close to one billion US dollars in grants and trust funds through to 2023.
However Tony de Brum, who is acting as an advisor for Kwajalein landowners, is questioning the legality of their stance.
"They can implement parts of the compact if they wish to, but constitutionally they cannot take land that does not belong to them beyond 2016 without the approval of the landowner."
Mr De Brum says they will not approve an extension of the present lease agreement beyond 2016 unless certain demands are met.
Landowners have rejected an American offer of a 15 million dollar a year rental for the missile site, demanding that it be increased to 19 point one million.
But he says there are other issues at stake, such as contamination, repatriation and resettlement.
The new Compact gives the United States use of the base until 2066.