Then, go to work on the jacket. Tree pitch is a natural resin containing what are called "dipertenes" and "tripertenes." Think "turpentine smell" and you'll get the idea. On the tree, these resins repel insects such as bark beetles, deter plant-eating creatures such as deer, and inhibit the growth of fungi and bacteria. Maybe you just leave the stuff on the jacket, so you won't be attacked by swarms of bark beetles, not to mention fungi and bacteria.
If you're still determined to rid the jacket of its stain, these resins are not water-soluble, so washing it in the washing machine will accomplish little. First, put the jacket in the refrigerator to stiffen the pitch, and then scrape off as much as you can with a dull knife. You have a few possibilities for your next line of attack. Spray the stain with Spot Shot ($4 per can at stores such as Target or Wal-Mart), an excellent carpet-stain remover that contains materials similar to the stuff used by dry-cleaners. If that doesn't work, then try the original formula of Goof Off, a paint remover (Goof Off 2 is water-based and not as effective against resins). It's pretty potent stuff, and really ought to do the trick. If this fails, then pull out the heavy artillery: a little acetone on a cotton rag. Be prepared for some color fading at that point, however.
It's also true that cooking oil will help loosen and dissolve the pitch. Soap does remove oil, so you could also rub a little Wesson on the pitch, then stick the jacket in the washing machine.
Note that the DWR (durable water-repellent) coating may also come off with the pitch. This can easily be restored with a little Gore ReviveX ($6), a spray-on DWR replacement.