There is a pile of stone dragons on the roof of someone else's house. Is it illegal for him to do so?

Not illegal.

Fengshui function of stone lions: 1. In people's folk life, stone lions are not only used to guard the gate, but also set up stone lions at rural intersections, which have the same function as Shi Gandang, and are used to guard houses, ward off evil spirits, suppress bad omen and protect village peace. Therefore, using stone lions to keep the gate away from evil spirits and resist the harm caused by demons and ghosts shows people's psychological demand for peace.

2. Forecast floods. In folklore, the stone lion has the function of predicting disasters. It is said that in the event of natural disasters such as floods or land subsidence, the eyes of stone lions will turn red or bleed, which is a sign of impending disaster and people can take refuge in an emergency. Here, the stone lion became a prophet of disaster.

3. Highlight dignitaries. In ancient times, stone lions were used as gatekeepers in palaces, palaces, offices and mansions, showing the power and dignity of their owners. For example, two pairs of stone lions guarding the gate of the imperial city on the Jinshui River in front of Tiananmen Square in Beijing reflect the supremacy of imperial power and the inviolability of gods.