
No need to oppose it if people are too scared / poor to try it. I also imagine there are better crops than hemp for paper. Lignocellulose (the type of plant matter used to make paper) typically makes up about the vast majority of the total dry matter in most plants. There are probably many other plants that produce the raw material more efficiently on a land and water basis with much less risk of getting outlawed.
I would bet that the processing is actually the much tougher problem to deal with than the growing of the plants as machinery is in general more expensive than plants and land.
It might even be cheaper to produce less plant matter on more lower quality ground than to use less land that is more ideal for growing. But I suspect it is just complacency on the part of the growers and / or paper pulp processors.
I imagine the people who own the land (ie. farmers) don’t have an interest in it because there isn’t an established industry to process it into products like cloth or rope or paper. This means they would have to buy the equipment not only to harvest / plant but also to process into usable material. If there was a pulp factory that would buy it from them they might plant it, but I doubt that any existing pulp factory would buy it as they would probably have to modify their production process slightly to make it into paper. Essentially it’s the chicken and the egg problem of farmers don’t have a market to sell it to, and factories can’t buy enough to justify converting the production process to use the new material.