However there are ways around it:

1. Don't use the VS SQL Server Project, but just create a normal class library project, add references as per usual and then manually create your assembly through CREATE ASSEMBLY. Make sure your referenced assemblies are in the same directory as your user assembly. The SQLCLR team has released some code that automatically creates procs/functions/triggers etc. when you run the CREATE ASSEMBLY code.

2. If you want to use the VS SQL Server Project you can create the assembly you want to reference in the database before you try to reference it. I.e: do a manual CREATE ASSEMBLY against the ManagedDTS.dll

3. Use my SQL Server VS templates and deploy task. This gives you the ability to reference what you want, and still get auto deployment. However, which-ever way to go, be careful with what you are doing. You don't want some code to compromise SQL Server!

The easiest way to be able to create an assembly as UNSAFE/EXTERNAL ACCESS you can do this:

1. Mark the database as trustworthy: ALTER DATABASE db_name SET TRUSTWORTHY ON 
2. Give the login of the owner of the database the right permissions: GRANT EXTERNAL ACCESS ASSEMBLY to userlogin.

That's it. You can now create an assembly as EXTERNAL ACCESS/UNSAFE. 

Are your SSL pages plagued by the IE warning "This page contains both secure and nonsecure items. Do you want to display the nonsecure items?"

Rather than changing all the links to https://, change them to just //

<img src="//www.domain.com/image.gif" alt="" />

Alternatively, if the images or scripts are located on the same domain, you can access them relatively, rather than absolutely:

<img src="image.gif" alt="" />

Using this method, the browser will know that it must load the image securely if the web page is being loaded securely but it will also load the image normally if the page is not being accessed securely. The image will still need to be available on the other server securely.