The Florida legislature has the power to change the law. This is why when the wording to dissolve the district was worded this way:
Notwithstanding s. 189.072(2), any independent special 23 district established by a special act prior to the date of 24 ratification of the Florida Constitution on November 5, 1968, 25 and which was not reestablished, re-ratified, or otherwise 26 reconstituted by a special act or general law after November 5, 27 1968, is dissolved effective June 1, 2023.
The "notwithstanding" means they can ignore previous laws, including the original charter. This is within their legislative power to do so.
However, the state legislature cannot violate the state constitution. Therefore, any challenge at the state level is going to have to hinge on the Florida Constitution.
This is why I highlighted this section of the state constitution:
Transfer of powers. — By law or by resolution of the governing bodies of each of the governments affected, any function or power of a county, municipality or special district may be transferred to or contracted to be performed by another county, municipality or special district, after approval by vote of the electors of the transferor and approval by vote of the electors of the transferee, or as otherwise provided by law.
Depending on one's interpretation, this could suggest that the state legislature has the power ("provided by law") to transfer the "function or power of a" "special district" to another special district "by law". The legislative passes laws. The legislature has the power.