My family used to live next to state land. The state can be very pissy about its land. If the fence line is on the state land, which it almost certainly is barring a surveying error when it was put up, it is entirely possible that if he fixed it, he would actually get in trouble with the state. Hopefully not actual legal trouble... but only hopefully, certainly not a "oh they would never bother". Oh they most certainly do sometimes decide to bother about the most random things.
My default presumption, without checking with them directly, is not only that it would not be allowed, but that this is also very much not a "better to ask forgiveness than permission" situation either. Even just asking the question can draw attention from them you may not want.
The ready accessibility of the land is advantageous in some ways, but as neighbors the state can be quite nasty. Your other neighbors don't tend to have anywhere near the regulatory firepower to make sure you comply with what they want.
My default presumption, without checking with them directly, is not only that it would not be allowed, but that this is also very much not a "better to ask forgiveness than permission" situation either. Even just asking the question can draw attention from them you may not want.
The ready accessibility of the land is advantageous in some ways, but as neighbors the state can be quite nasty. Your other neighbors don't tend to have anywhere near the regulatory firepower to make sure you comply with what they want.