I would be very surprised if, ultimately, Delaware's authority under the Coastal Zone Act isn't pre-empted by the federal permits, and federal authority to regulate interstate commerce on navigable waterways.
Coincidentally, that doctrine goes all the way back to a John Marshall decision on the subject of building a dam on Blackbird Creek.
http://press-pubs.uchicago.edu/founders/documents/a1_8_3_commerces20.html
The act of assembly by which the plaintiffs were authorized to construct their dam, shows plainly that this is one of those many creeks, passing through a deep level marsh adjoining the Delaware, up which the tide flows for some distance. The value of the property on its banks must be enhanced by excluding the water from the marsh, and the health of the inhabitants probably improved. Measures calculated to produce these objects, provided they do not come into collision with the powers of the general government, are undoubtedly within those which are reserved to the states.
...
The counsel for the plaintiffs in error insist that it comes in conflict with the power of the United States "to regulate commerce with foreign nations, and among the several states." If Congress had passed any act which bore upon the case, any act in execution of the power to regulate commerce, the object of which was to control state legislation over those small navigable creeks into which the tide flows, and which abound throughout the lower country of the middle and southern states; we should feel not much difficulty in saying that a state law coming in conflict with such act would be void. But Congress has passed no such act. The repugnancy of the law of Delaware to the Constitution is placed entirely on its repugnancy to the power to regulate commerce with foreign nations and among the several states; a power which has not been so exercised as to affect the question.
The difference here is that LNG importation and the facility permits *are* the subject of federal regulation of foreign and interstate commerce. So you have a conflict between the federal government granting permission to a project involving an interstate navigable waterway, and the state government asserting authority to stop it.
Gibbons v. Ogden is right on point. New York had granted a monopoly to the Fulton company to operate steamboats in New York's waters, including the Hudson Bay. A New Jersey company sought to also operate steamboats from New Jersey, crossing New York's waters.
http://www.tourolaw.edu/patch/Gibbons/This court is of opinion that so much of the several laws of the state of New York as prohibits vessels, licensed according to the laws of the United States, from navigating the waters of the state of New York, by means of fire or steam, is repugnant to the said Constitution and void.The amazing thing about the BP project is that the LNG tankers draw about 36 feet, and the river channel depth is maintained at about 40 feet by dredging. The Salem/Hope Creek complex has igniters surrounding it, so that any leak will be lit and blown back at Port Penn, in order to keep the plants safe. But, along with closing the Del. Mem. Br. every time one of these things comes through, one wonders whether using a site further south, and running a pipeline, might be a better idea.