you don't even have to do that. if you have a retail box copy, you can install and play without registering online. you do have to register in order to access patches, updates, and new content for free. only games downloaded from impulse require you to register beforehand, because you need to in order to download the files.
regarding wardell's comment about the lawsuit, i agree with others here that the lawsuit is perfectly valid. EA did not disclose the presence of secuROM to the public at large, which is blatatnly anti-consumer. it may even run afoul of consumer protection laws. we'll have to see what the courts decide.
you can -- its called a a receipt. that transaction is a form of contract between the buyer and seller. within that transaction are your first-sale and fair-use rights -- which includes the ability to do what you want with the product without making additional copies (beyond copies for backup and personal, non-commercial use) of the content. software companies have been trying to change this for decades by calling sales "licenses" rather than sales. and courts have decides that simply calling a sale a "license" doesn't make it one.
i'd say that the law isn't clear on this because the nature of digital content means that existing copyright laws don't perfectly cover what people can do -- digital content essentially removes the physical limitations of analog content that copyright law relies upon to prevent unwarranted copying of content.