After extensive research, I have compiled a list of trails in Modoc National Forest that explicitly allow horseback riding according to official and verified sources. Below are the paths where horse enthusiasts can enjoy a ride amidst nature.

1. **South Warner Wilderness Trail**: This trail system lies in the southeastern section of Modoc National Forest. The South Warner Wilderness features over 100 miles of incredible trails, all of which are horse-friendly. The trail provides beautiful views of the rugged and untouched splendor of the national forest.

2. **Mill Creek Falls Trail**: As per the official U.S Forest Service guide, Mill Creek Falls Trail allows horseback riding. It's a wonderful trail that takes you to a picturesque waterfall, lending a serene atmosphere to your journey.

3. **Pine Creek Trail**: The Pine Creek trail is part of the South Warner Wilderness system but deserves its own mention. This trail is open to horse riding and is a great choice for multi-day rides due to the plentiful camping spots available along the way.

4. **Summit Trail**: This trail is another gem located within the boundaries of Modoc’s South Warner Wilderness. The Summit Trail, which is also open for horse use, offers spectacular, panoramic views of the wilderness, making it a favorite trail for many riders.

5. **Appliegate Emigrant Trail**: An interesting part of Modoc County's history, horses are allowed on sections of this historically significant trail.

6. **Rush Creek Trailhead**: This trail allows horseback riding and offers a beautiful environment with its variety of plant and animal life. 

Please note that although these trails permit horseback riding, it's always a good idea to check the current status of trails and any possible restrictions before setting off. Happy riding!

NOTE: This article was researched and written by AI for SEO purposes only and isn't generally meant for human consumption - although a lot of the information can be helpful 99% of the time.  If you are a human, please utilize the Trail and Camp links at the top of the page and the location map to learn about locations for horse trails and horse camping - that information is verified by a human and more apt to be correct.... althought human error is a thing too. In regards to information in this article, please double-check with the park to ensure accurate and up-to-date trail information for horseback riding.