The Army Corps in conjunction with the US EPA does likely indeed have a way to "defend". By federal law, an Army Corps permit is required for any construction activity affecting the waters of the United States. Absent such a permit, the Corps or EPA can easily obtain an injunction from a federal court prohibiting construction until the necessary permit is issued. The very recent US Supreme Court Opinion in SACKETT ET UX . v. ENVIRONMENTAL PROTECTION AGENCY ET AL., while it limited somewhat the definition of waters of the USA, stated: "In sum, we hold that the CWA extends to only those wetlands that are “as a practical matter indistinguishable from waters of the United States.” Rapanos, 547 U. S., at 755 (plurality opinion) (emphasis deleted). This requires the party asserting jurisdiction over adjacent wetlands to establish “first, that the adjacent [body of water constitutes] . . . ‘water[s] of the United States,’ (i.e., a relatively permanent body of water connected to traditional interstate navigable waters); and second, that the wetland has a continuous surface connection with that water, making it difficult to determine where the ‘water’ ends and the ‘wetland’ begins.”
The Massachusetts swamp in question is clearly has streams, rivers and ponds with continuous surface connection with that water and the swampland and the precise boundary cannot be determined. The navigable water definition has long been held to include navigation in commerce at any time in the past, including the era of canoes used as the vessels in commerce. See:
https://www.supremecourt.gov/opinions/2 ... 4_4g15.pdf