Kensington and Chelsea Council asked the owners of The Zephyr and The Pacifica to move them back in May.
The authority says the size of the boats has significantly changed the landscape and is harming the appearance of the conservation area.
An appeal against the enforcement action was then lodged by the owners, the Chelsea Yacht and Boat Company.
The Planning Inspectorate is due to make a decision on whether the boats can stay within the next four weeks.
