from the 5th Amendment:

Amendment V - Trial and Punishment, Compensation for Takings. Ratified 12/15/1791.

No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.

No doubt, some will say that since the land "owners" aren't actually being deprived of their property (they get to pay for it, after all) and that 65% of their land isn't actually being taken for public use, then this law should be OK. I disagree. Most people accept some limitations on what people can do with their own property, such as not allowing a toxic waste dump, but declaring that someone has to pay for and maintain 65% of their property as others dictate (deliberate choice of word there), then freedom is lost. To me, if you're going to deny people fair use of their property, then the 5th amendment compels you to pay just compensation.