It is safe to suppress a warning from this rule when the library or application is intended for a limited local audience and will therefore not be localized.

This is actually incorrect. If making security decisions based on the result or doing path comparisons, you should explicitly specify a string comparison, passing one of StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase.

The following example shows a method that incorrectly compares the start of an URL:

[C#]

using System;
using System.Globalization;
using System.Threading;

namespace Samples
{
    class Program
    {
        static void Main(string[] args)
        {  
            Thread.CurrentThread.CurrentCulture = new CultureInfo("tr-TR");

            string url = "file:///C|/MyFile.txt";

            if (string.Compare(url, 0, "FILE:", 0, 5, true) == 0)
            {
                Console.WriteLine("File path");
            }
            else
            {
                Console.WriteLine("Something else");
            }
        }
    }
}

The above outputs the following:

Something else

To fix the above violation specify StringComparison.OrdinalIgnoreCase.

The following example shows this.

[C#]

using System;
using System.Globalization;
using System.Threading;

namespace Samples
{
    class Program
    {
        static void Main(string[] args)
        {

            Thread.CurrentThread.CurrentCulture = new CultureInfo("tr-TR");

            string url = "file:///C|/MyFile.txt";

            if (string.Compare(url, 0, "FILE:", 0, 5, StringComparison.OrdinalIgnoreCase) == 0)
            {
                Console.WriteLine("File path");
            }
            else
            {
                Console.WriteLine("Something else");
            }
        }
    }
}

The above outputs the following:

File path

By default, most of the comparison methods on the String class (such as String.Compare) perform a linguistic comparison. This is in constrast to String.Equals, which, by default, performs a non-linguistic (ordinal) comparison.
Because these linguistic comparisons use the thread's current culture (retrieved from CultureInfo.CurrentCulture), their behavior can vary based on the current user's locale settings. To make it clear which comparison method a particular call site makes, use an overload that takes a StringComparison value. This is especially important if comparing paths, registry keys, environment variables, or making security decisions based on the result.

For more information, see the following article:

New Recommendations for Using Strings in Microsoft .NET 2.0
http://msdn2.microsoft.com/en-us/library/ms973919.aspx